Hybrid functionals studies of structural and electronic properties of ZnxCd(1−x)S and (ZnxCd1−x)(SexS1−x) solid solution photocatalysts

The structural and electronic properties of the wurtzite ZnxCd1−xS and (ZnxCd1−x)(SexS1−x) alloys are calculated using density functional theory calculations with HSE06 hybrid exchange-correlation functional. Special quasirandom structures are used to describe the disordered alloys, for x = 0.125, 0.25, 0.375, 0.5, 0.625, 0.75 and 0.875, respectively. Our calculations reveal that ZnxCd1−xS alloy with the appropriate Zn doping concentration not only causes the elevation of the conduction band minimum energy, but also increase the mobility of photogenerated holes and electrons, which well explains the high photocatalytic activity and stability of Zn0.2Cd0.8S alloy under a long-term light irradiation. Compared with ZnxCd1−xS alloy, (ZnxCd1−x)(SexS1−x) alloy holds greater potential to simultaneously meet band gap, band edge, and mobility criteria for water splitting. Theoretical results predict that (ZnxCd1−x)(SexS1−x) alloy with the ZnSe concentration in the range from 0.38 to 0.75 could be a more promising candidate than Zn0.2Cd0.8S alloy for photoelectrochemical hydrogen production through water splitting.

▶ Lattice parameters and band gaps of ZnxCd1−xS and (ZnxCd1−x)(SexS1−x) are nicely reproduced. ▶ Our results rationalize experimental results which showed that Zn0.2Cd0.8S exhibits higher photocatalytic activity than CdS. ▶ (ZnxCd1−x)(SexS1−x) holds great potential to simultaneously satisfy the criteria for water splitting.